The present invention relates to a method and apparatus for detecting a mobile phone in an Idle State, and in particular, for generating an alarm when the phone in Idle State enters an area where the usage of the mobile phone is prohibited.
A typical cellular telephone system includes a plurality of base stations, each of which services a geographical cell of a small-scale area, thereby providing coverage over a wide area encompassed by a multiplicity of such cells. The base stations are centrally controlled by a mobile switching center (MSC) so that a mobile phone subscriber can maintain communication when moving between cells.
Cellular phone systems are advantageous in that they provide service to mobile phone subscribers within any cell covered by the system. However, a drawback to the cellular system is that it may do harm to the public order in an area where usage of the mobile phone is prohibited. For example, if a mobile phone rings while receiving a call in a concert or exhibition hall, the resulting noise is a disturbance to the performance. Additionally, mobile phone signal transmissions may interfere with the operation of sensitive electronic equipment such as in a hospital or an airplane. Such electronic equipment can be adversely affected by traffic channel signals as well as control channel signals, such as those sent back and forth between mobiles and base stations during the call set-up process, or during the registration process when a mobile phone is first turned on.
One conventional technique to restrict use of a mobile phone in a specific area is to employ an apparatus for generating an interference signal to essentially xe2x80x9cjamxe2x80x9d the mobile phone and thereby prevent it from operating properly. FIG. 1 shows an embodiment illustrating a prior art apparatus for generating an interference signal for this purpose. An apparatus 11 generates an RF interference signal so as to prevent use of a mobile phone inside a building 10. However, in general, buildings have windows or other entrances for radio waves from the exterior. As such, with the approach of FIG. 1, it is impossible to completely shut out radio frequency entering from external base stations attempting to communicate and/or send control channel signals to mobile phones within the building. Another problem is that the RF interference signal generated by apparatus 11 may cause other electronic equipment to malfunction.
Another prior art technique for restricting mobile phone use involves the deployment of magnetic material detectors in selected locations to detect the presence of mobile phones, which have magnetic material therein. FIG. 2 shows an embodiment of an apparatus for detecting magnetic substances. When a body possessing an object 24 having magnetic components enters through an entrance 21, a magnetic detector 22 established inside the entrance 21 detects the magnetic components and transmits an alarm signal to an alarm generator 23, which then sounds an alarm. A drawback to this approach is that it will detect such phones and sound an alarm regardless of whether the phones are in use.
Traditionally, in such restricted use environments, announcements are made to the public exhorting mobile phone owners to shut off power to their phones, but inevitably, some phones remain turned on. Hence, there is a need for a system that automatically detects use of a mobile phone in the Idle State in public areas.
The present invention is directed to a method and apparatus for detecting the presence of a mobile phone in an Idle State, in which the mobile phone is powered up but not performing communication. Embodiments of the invention render it possible to detect, for example, a mobile phone in the Idle State within a specific indoor area, or upon entering an entranceway.
In an illustrative embodiment of the invention, there is provided an apparatus for detecting a mobile phone in an Idle State, which apparatus includes a signal-generating unit that generates a pseudo base station signal for transmission to a mobile phone in a detection area. A detecting unit detects a response signal that the mobile phone transmits in response to the pseudo base station signal. An alarm-generating unit generates an alarm when the detecting unit detects the response signal. Preferably, the pseudo base station signal is an overhead channel signal that includes new zone information, such that the mobile phone responds by transmitting a location registration signal which is detected by the detecting unit. The method and apparatus are particularly advantageous in a code division multiple access (CDMA) system.
The apparatus may further include a GPS receiver for receiving time information from a satellite and generating a system reference clock, and circuitry for receiving and analyzing neighboring base station information transmitted by such base stations in overhead channels. In this case, the signal generating unit generates the pseudo base station signal using the system reference clock and neighboring base station information. The pseudo base station signal may be transmitted in a plurality of frequency channels of the communication system to ensure successful reception by the mobile station. In addition, the detection unit may sequentially tune to a plurality of access channels to ensure reception of the location registration signal.
Other objects and advantages of the invention will become apparent upon reading the detailed description and upon reference to the drawings.